Symbol display tube with auxiliary electrode

ABSTRACT

An evacuated envelope having a transparent display face contains a plurality of selectively energizable, phosphor-coated anode display elements for presenting a symbol display, with an auxiliary electrode disposed either behind or coplanar with said display elements and electrically insulated therefrom. A cathode comprising one or more filaments is situated in front of said display elements, i.e., between the display elements and the display face of the envelope, to provide a direct electron beam to the phosphor-coated surfaces of the display elements.

0 United States Patent 1191 1111 3,780,326 Raago Dec. 18, 1973 SYMBOLDISPLAY TUBE WITH 3,619,694 11/1971 Tanji 313/1095 AUXILIARY ELECTRODE3,584,252 6/1971 Du Bois, Jr. 313/1095 317,633 5/1885 Edison 313/278 xInventor: Rein Raago, Morristown, NJ.

Wagner Electric Corporation, Newark, NJ.

Filed: Aug. 25, 1971 Appl. No.: 174,666

Assignee:

References Cited UNITED STATES PATENTS 6/1972 Shimada 313/108 R X12/1968 Frouws et a1. 313/1095 Primary Examiner-Palmer C. DemeoAttorney-William D. Lucas [5 7] ABSTRACT An evacuated envelope having atransparent display face contains a plurality of selectivelyenergizable, phosphor-coated anode display elements for presenting asymbol display, with an auxiliary electrode disposed either behind orcoplanar with said display elements and electrically insulatedtherefrom. A cathode comprising one or more filaments is situated infront of said display elements, i.e., between the display elements andthe display face of the envelope, to provide a direct electron beam tothe phosphor-coated surfaces of the display elements.

8 Claims, 2 Drawing Figures PAIENTEDntc 18 ms INVENTOR FEW 64/1 0 WATTO. NEYS /1/VODE- Tmqb- P04 55 E/VEEA roe SYMBOL DISPLAY TUBE WITHAUXILIARY ELECTRODE CROSS-REFERENCES TO RELATED APPLICATIONS The presentapplication relates to an improved embodiment of the symbol display tubedisclosed in copending application Ser. No. 66,403 filed Aug. 24, 1970in the name of Rein Raago, which issued as U. S. Pat. No. 3,688,147 onAug. 29, 1972.

BACKGROUND OF THE INVENTION l. Field of the Invention The presentinvention is properly classifiable in class 313, subclass 109.5(Electrical Lamp Discharge Devices with Indicia or Scale).

2. Description of the Prior Art Various circuits have been devised tostrobe a multitube array comprising tubes of the type disclosed in therelated applications cited above. Specifically, U.S. Pat. No. 3,555,544issued on Jan; 12, 1971 upon an application filed in the name of Carl E.Atkins and US. Pat. No. 3,553,525 issued on Jan. 5, 1971 upon anapplication filed in the name of Francis A. MCGUIIk, Jr. each disclosescircuitry for strobing the symbol display tube disclosed in the relatedapplications by turning the cathode-energizing voltage on and off. Thisstrobing technique requires more complex circuitry than is necessarywith applicants symbol display tube. Such simplified control circuitryas is disclosed herein affords the economies of fewer components andreduced consumption of electrical power.

US. Pat. No. 3,584,252 issued on June 8, 1971 upon an application filedin the name of Richard DuBois, Jr. discloses a symbol display tube inwhich an electrically conductive layer is disposed about the displayelements on a surface of the transparent envelope. This device isdescribed as being operative in cooperation with related circuitry toperform a blanking function by placing the shielding layer at a negativepotential with respect to the cathode. However, because of the variableand relatively large distances between the display elements and thesurface of the conductive layer, this prior art device is unable toperform with the speed and uniform effectiveness of applicants device.

SUMMARY OF THE INVENTION Applicants invention is embodied in and carriedout by a symbol display tube having a plurality of selectivelyenergizable display elements coated with phosphorescent material toenable the formation of a predetermined group of symbols, with astrobbing or auxiliary electrode disposed either behind or coplanar withsaid display elements and electrically insulated therefrom to enablehigh speed, time-sharing operation of the complete display formed by aplurality of such symbol display tubes with relatively simple externalcircuitry having low power requirements.

BRIEF DESCRIPTION OF THE DRAWING A more complete understanding of thepresent invention may be obtained by referring to the accompanyingdrawing, of which:

FIG. 1 is an isometric view of a display tube constructed in accordancewith the present invention, partly broken away to illustrate the spatialrelationships and cross-sections of tube elements; and

FIG. 2 is a block diagram of a circuit incorporating a plurality ofdisplay tubes constructed in accordance with the present invention.

DESCRIPTION OFTHE PREFERRED EMBODIMENTS Referring now specifically toFIG. 1, the display tube 10 may be seen to comprise a composite envelopehaving a flat, transparent display face 12 and a dished, substantiallyrectangular support member 14 which is preferably opaque. Seven anodedisplay elements 16A, 16B, 16C, 16D, 16E, 16F, and 166 in a figure-8array are each formed by a stick-shaped conductive layer deposited onthe floor (major inner surface) of support member 14 with an overlying,coextensive phosphor coating. Optionally, a period or decimal point maybe formed in the display by another SLllCh anode display element 16H. Astrobing or auxiliary electrode 17 is also disposed on the floor ofsupport member 14, and surrounds each of the anode display elementsl6A-H while being insulatedly spaced therefrom. When the electrode 17 isplaced at a positive potential with respect to the cathode 18, it willact as an accelerator of electrons, resulting in a brighter display.Thus, the electrode 17 can be used as a means to control displayintensity. Also, when thus operated, electrode l7 acts as a means forproducing uniform current density over a relatively large area,especially when the electrons are emitted from a one-or two-line source.When placed at negative potential, electrode 17 will prevent the flow ofelectrons to the anode display elements l6A-H. Thus, the electrode 17may also serve to perform a strobing function. A cathode 18 comprising asubstantially parallel pair of filaments 18A and 18B is disposed betweenthe display face 12 and the display elements l6A-H to provide an evendistribution of high-velocity electrons to each of the display elements.The cathode filaments 18A, 18B lie in a plane which is substantiallyparallel to the plane in which the display elements lie. A plurality ofconnecting pins 20A, 20B, 20C, 20D, 20E, 20F, 20G and 20H are connectedto the conductive portions of display elements 16A, 16B, 16C, 16D, 16E,16F, 16G and 16H, respectively, and extend through the insulatingsupport member 14 to enable electrical connection of the displayelements to an external control circuit. The connecting pins 22, 24 and26 are attached to the terminals of cathode l8 and extend through thesupport member 14 for connection to the source of electrical power. Asshown, the strobing or auxiliary electrode 17 is insulatedly spaced awayfrom the pins 22, 24 and 26. The upper ends of filaments 18A, 18B areconnected to the ends of filament spring 23, which in turn is connectedperpendicularly to the upper connecting pin 22. The lower ends offilaments 18A, 18B are connected to the lower connecting pins 24, 26,respectively. This arrangement makes it possible to energize the cathodefilaments as either parallel-connected resistances or series-connectedresistances. With one terminal of a source of electromotive force (EMF)connected to pin 22, and the other terminal connected to pins 24, 26,the filaments 18A, 18B are energized as parallel-connected resistances.With one terminal of a source of EMF connected to pin 24 and the otherterminal to pin 26, pin 22 being left floating or unconnected, thefilaments 18A, 18B are energized as seriesconnected resistances.Connecting pin 28 is connected to electrode 17, and extends through thesupport member 14 to enable electrical connection to external controlcircuitry. An exhaust tube 30 may be either integrally formed with thesupport member 14 from the same material, or formed from a differentmaterial and then joined with support member 14 in the region ofaperture 32 extending through the thickness of support member 14.

Referring now specifically to FlG. 2, the circuit shown therein includesthree symbol display tubes l1, l0-2 and -3 constructed in accordancewith the foregoing description of the tube shown in FIG. 1. Each ofthese tubes has its anode display elements 16 connected to theanode-cathode power supply and switching circuit 34. The correspondinganodes in each of the three tubes are connected in parallel with oneanother and to a terminal of the power supply and switching circuit 34.The cathodes of the three tubes are also connected in parallel andenergized by power supply and switching circuit 34. Pulse generator 36draws its power and receives synchronizing signals from power supply andswitching circuit 34, and normally maintains the strobing or auxiliaryelectrodes 17 in the three tubes at a voltage which is sufficientlynegative to prevent the flow of emitted electrons from the cathodes 18to any energized anodes 16. In operation, a first group of anode displayelements 16 is placed at a positive potential with respect to thecathode 18 for a first time interval A 1. During this time period A 1 t,the pulse generator 36 places only the electrode 17 of tube 10-1 ateither ground or positive potential. Thus, the accelerated flow ofelectrons from the cathode 18 to the energized anode display elements 16in tube 10-1 is unimpeded, and a first symbol will be displayed by thisfirst tube. However, even though the corresponding parallel-connectedanode display elements in tubes 10-2 and 10-3 are also placed at apositive potential with respect to their associated cathodes, thesetubes are blanked because their electrodes 17 remain at their normalnegative potential to prevent the flow of electrons from the cathodes tothe energized anode display elements. During a second time interval A 1,a second group of anode display elements in each of the three tubes isenergized, and only the electrode 17 of tube 10-2 is placed at eitherground or positive potential by the pulse generator 36. Thus, a secondsymbol will be displayed by the tube 10-2 as a result of the acceleratedflow of electrons from its cathode to its energized anodes. Tubes 10-1and 10-3 will be blanked during the interval A because their electrodes17 are at their normal negative potential. Finally, during a third timeinterval A a third group of anode display elements 16 in each of thethree tubes is energized and only the electrode 17 of tube 10-3 isplaced at either ground or positive potential by pulse generator 36.Thus, a third symbol will be shown by tube 10-3, while tubes 10-1 and10-2 are blanked by the negative potential placed on their respectiveelectrodes 17. This sequence is repeated at a sufficiently high rate togive the appearance that the tubes 10-1, 10-2 and 10-3 are eachconstantly energized.

The advantages of the present invention will be apparent to thoseskilled in the art, as well as changes which could be made in theforegoing embodiments without departing from the spirit and scope of theinvention. For example, the anode display elements may be coplanar withor on either side of the strobing or auxiliary electrode. Also, insteadof utilizing two or more discrete parallel cathode filaments, a single,a continuous filament having two or more portions thereof similarlyarrayed could be advantageously utilized. Also, instead of arrangingeither the discrete cathode filaments or sections of a continuouscathode filament in parallel spatial relationship, a V-shaped (twofilaments or filament segments) or N-shaped (three filaments or filamentsegments) array could be advantageously employed. With such arrays, themutual repelling forces would be greater in the region where thefilaments or filament segments are in close proximity and weaker in theregion where they are farther apart, thus effecting spreading of theelectron streams to the degree required by the spacing at any particularlevel of the display. It will be readily apparent that, in an embodimentemploying a continuous, series-energized cathode filament, a break inthat filament will completely disable the source of the electrons. Inmany applications, it is far more hazardous to have an erroneousreadout, which might occur if one of several discrete cathode filamentsfailed, than it would be to have no readout at all. In the lattersituation, an observer will at least know that the display tube is notfunctioning, whereas with an erroneous readout, an observer might haveno reason to believe that there is a display tube malfunction.

Therefore, it should be understood that the present invention is not tobe limited to the foregoing description of the specific embodimentsthereof, but is to be determined by the spirit and scope of theaccompanying claims.

What is claimed is:

l. A display tube comprising:

1. an evacuated envelope including a transparent display face and asupport member;

2. a plurality of anode display elements each of which is coated with aphosphor, all disposed in a first plane within said envelope so as toform any of a desired group of symbols by selectively energizing saidanode display elements;

3. an electrode, disposed in a second plane within said envelope,surrounding each of said anode display elements and being electricallyinsulated therefrom;

4. an electron-emissive cathode disposed between said transparentdisplay surface and said plurality of anode display elements; and

5. a plurality of connector means extending through said support memberand operative to enable electrical connection of said anode displayelements, said electrode and said cathode to external control circuitry.

2. The display tube according to claim 1 wherein said first plane inwhich said anode display elements are disposed is coincident with saidsecond plane in which said electrode is disposed.

3. The display tube according to claim 1 wherein said support member issubstantially rectangular and dished to form a floor therein, and saidtransparent display face is flat.

4. The display tube according to claim 3 wherein said electrode isdisposed on said floor of said support member.

5. The display tube according to claim 3 wherein said anode displayelements are disposed on said floor of said support member.

6. The display tube according to claim 1 wherein said is mounted, andextending through said support electron emissive cathode comprises atleast first and member; and second filaments spaced apart in a thirdplane substan- 3. second and third connecting pins extending tiallyparallel to said first plane in which said anode disthrough said supportmember and having the secplay elements are disposed. 5 0nd adjacent endsof said first and second fila- 7. The display tube according to claim 6wherein said ments, respectively, connected thereto. plurality ofconnector means includes: 8. The display tube according to claim 1wherein l. a filament spring disposed within said envelope seven anodedisplay elements are arranged in a figureand having the first adjacentends of said first and eight pattern for forming the digits from 0 to 9,inclusecond filaments connected thereto; 10 sive.

2. a first connecting pin on which said filament spring

1. A display tube comprising:
 1. an evacuated envelope including atransparent display face and a support member;
 2. a plurality of anodedisplay elements each of which is coated with a phosphor, all disposedin a first plane within said envelope so as to form any of a desiredgroup of symbols by selectively energizing said anode display elements;3. an electrode, disposed in a second plane within said envelope,surrounding each of said anode display elements and being electricallyinsulated therefrom;
 4. an electron-emissive cathode disposed betweensaid transparent display surface and said plurality of anode displayelements; and
 5. a plurality of connector means extending through saidsupport member and operative to enable electrical connection of saidanode display elements, said electrode and said cathode to externalcontrol circuitry.
 2. a plurality of anode display elements each ofwhich is coated with a phosphor, all disposed in a first plane withinsaid envelope so as to form any of a desired group of symbols byselectively energizing said anode display elements;
 2. The display tubeaccording to claim 1 wherein said first plane in which said anodedisplay elements are disposed is coincident with said second plane inwhich said electrode is disposed.
 2. a first connecting pin on whichsaid filament spring is mounted, and extending through said supportmember; and
 3. second and third connecting pins extending through saidsupport member and having the second adjacent ends of said first andsecond filaments, respectively, connected thereto.
 3. The display tubeaccording to claim 1 wherein said support member is substantiallyrectangular and dished to form a floor therein, and said transparentdisplay face is flat.
 3. an electrode, disposed in a second plane withinsaid envelope, surrounding each of said anode display elements and beingelectrically insulated therefrom;
 4. an electron-emissive cathodedisposed between said transparent display surface and said plurality ofanode display elements; and
 4. The display tube according to claim 3wherein said electrode is disposed on said floor of said support member.5. The display tube according to claim 3 wherein said anode displayelements are disposed on said floor of said support member.
 5. aplurality of connector means extending through said support member andoperative to enable electrical connection of said anode displayelements, said electrode and said cathode to external control circuitry.6. The display tube according to claim 1 wherein said electron-emissivecathode comprises at least first and second filaments spaced apart in athird plane substantially parallel to said first plane in which saidanode display elements are disposed.
 7. The display tube according toclaim 6 wherein said plurality of connector means includes:
 8. Thedisplay tube according to claim 1 wherein seven anode display elementsare arranged in a figure-eight pattern for forming the digits from 0 to9, inclusive.